The present invention relates to a rescue elevator system, comprising a rescue ladder and an elevator running on rails on a top side of the rescue ladder, according to the features of the preamble of claim 1.
Rescue ladders, like telescopic turnable ladders mounted on firefighting vehicles, are often equipped with rescue elevators that can run along the extension length of the ladder up to their movable free end. Persons to be rescued can enter the elevator at its end position at the free end of the ladder to be transported safely down to the ground. The elevator generally comprises a chassis with rollers running on the rails of the rescue ladder, and a cage mounted on the chassis for accommodating passengers. For driving the elevator, a rope is provided that is pulled by means of a rope winch provided at the mounting of the ladder. The rope is guided from the rope winch over at least one deflection roller towards a suspension point at the elevator. The deflection roller is disposed below the rails at or near the free end of the rescue ladder. By this deflection roller, the pulling force of the rope winch is deflected like in a classical pulley tackle such that it acts on the elevator to pull it towards its top end position. The end of the elevator approaching the free end of the ladder during this movement shall be designated in the following as its leading end, while the end of the elevator averted from the free end of the ladder shall be referred to as the trailing end.
When the elevator approaches its top end position, the transmission of the pulling force to the suspension point becomes increasingly disadvantageous. This is because in the common suspension systems, the rope sections running to and from the deflection roller include an angle of increasing size, with the consequence that with increasing pulling height there is an increasingly growing force component acting on the suspension point towards the bottom side of the ladder opposite to the rails. At the same time, the remaining force component acting to pull the elevator towards its end position is rapidly decreasing. With common elevators whose suspension point is located near their leading end in the pulling movement, it is practically impossible to reach the end of the rescue ladder where the deflection roller is located, because the force components acting perpendicular to the rails tend to deform the framework of the ladder and to pull the rescue elevator onto the rails, instead of supporting its sliding movement. Moreover, there is another disadvantageous effect by this unfavourable load transmission, because forces are generated to raise the elevator from the rails so that its running characteristics are impaired.
On the other hand, it is desired to move the elevator as far as possible towards the free end of the rescue ladder, where a rescue cage is usually mounted, to facilitate a safe passage of persons from the rescue cage into the elevator, in particular inexperienced persons with injuries, physical or mental restrictions, etc.